I noticed that the Github Action caching wasn't working, so I added this
setting to fix it.
https://github.com/actions/setup-go#caching-dependency-files-and-build-outputs
If the cache is populated the tests now take 5 minutes to run (down from
18m).
The one downside is that caching will also cache the test results (along
with the dependencies) so this change adds a `--count=1` to the `go
test` commands to ensure that the go test doesn't use a cached result.
e1cb498992